docs: def concat(self, enumerable):
          """
          Adds enumerable to an enumerable
          :param enumerable: An iterable object
          :return: new Enumerable object
          """
          if not isinstance(enumerable, Enumerable):
              raise TypeError(
                  u"enumerable argument must be an instance of Enumerable"
              )
          return Enumerable(itertools.chain(self._data, enumerable.data))